One metric for these phenomena is dubbed the "Boulder" type and uses the Wolf formula, while another
One metric for these phenomena is dubbed the "Boulder" type and uses the Wolf formula, while another type is called "International" and compiles information from more sources. The geographical distribution of these roughly corresponds to the appearance of a butterfly. One pattern associated with them is the Schwab Cycle and a decrease in their number, called the Maunder Minimum, contributed to the Little Ice Age. The dark central region of these objects called the umbra, in contrast with the lighter penumbra. These objects are caused by their namesake star's magnetic field welling up to the visible surface. For 10 points, identify these dark regions on the surface of the sun.
One metric for these phenomena is dubbed the "Boulder" type and uses the Wolf formula, while another type is called "International" and compiles information from more sources.
{Sunspots} [accept {starspots} - they {recently discovered} some on other {stars} as {well}]